Array Buffers

An ArrayBuffer buffer holds an array and a size. Most operations on
an array buffer have the same speed as for an array, because the
operations simply access and modify the underlying
array. Additionally, array buffers can have data efficiently added to
the end. Appending an item to an array buffer takes amortized constant
time. Thus, array buffers are useful for efficiently building up a
large collection whenever the new items are always added to the end.